The teachings of the Catholic Faith are generally on the topic of faith and morals. However, some teachings are on the topic of history, e.g. that the Fall from grace was an historical event, that the exodus of Israel from slavery in Egypt to the Promised Land was an historical event, that the Crucifixion and Resurrection and Ascension were historical events. Other teachings are matters of faith, but include certain assertions in the realm of science, such as, on the creation of the universe, that God created heaven and earth. Christians are obliged to reject any and all hypotheses, theories, and claims of alleged fact, which directly and irreconcilably contradict the teachings of the Tradition, Scripture, Magisterium on any subject.
“In ‘The Grand Design,’ co-authored with U.S. physicist Leonard Mlodinow, Hawking says a new series of theories made a creator of the universe redundant, according to the Times newspaper which published extracts on Thursday. ‘Because there is a law such as gravity, the universe can and will create itself from nothing. Spontaneous creation is the reason there is something rather than nothing, why the universe exists, why we exist,’ Hawking writes.” (http://www.reuters.com/article/idUSTRE6811FN20100902)
The claim that the universe created itself is not a new scientific claim. However, any Christian who believes such a claim commits the sin of heresy. The Faith teaches that God created heaven and earth, i.e. the Universe. Only two types of things have existence: God and His Creation. God is uncreated. All else is created by God. (Evil is a privation of good, and so evil does not have existence; it is a deprivation of some quality in something that does exist.) The scientific theory that the universe created itself, or came into existence on its own, is an attack on Christianity and Judaism and Islam. It is essentially a claim that we are not created by God, and therefore that we do not belong to Him. It tends toward agnosticism, in that it makes God irrelevant.
The claim that God did not create the Universe, implies all the teachings based on natural law are fallacies. For those teachings are based on the idea that Creation is a reflection of the goodness of God, since it is His Creation. The claim that God did not create the universe implies that we are not made in the image of God. The claim that God did not create the universe implies that the teachings of Tradition, Scripture, Magisterium contain falsehoods about God.
Catholic scientists and the Catholic faithful in general are not free to believe any scientific theory, even if reason seems to support that theory. Certain scientific theories are heretical, and any Catholic who chooses to adhere to such a theory, knowing that it contradicts the definitive teachings of the Faith, commits the sin of formal heresy and is automatically excommunicated by the very nature of the act of heresy.